Combustion control system



July 24, 1934.

P. s. DICKEY COMBUSTION CONTROL SYSTEM Filed Oct. 27, 1931 2 Sheets-Sheet 1 v 45 INVENTOR 6 Paul S.D1c

Fig.2,

key.

ATTORNEY July 24, 1934. P. s. DICKEY 1,967,983

COMBUSTION CONTROL SYSTEM Fi led Oct. 27, 1931 2 sham-sheet 2 63 in gas 62. 64

F. 4 6 r INVENTOR Y u er- Paul S.D1Cke I 7 6 BY 5O 44,

ATTORNEY Patented July 24, 1934 PATENT OFFICE COMBUSTION common srs'roM Paul S. Dickey, Cleveland, Ohio, assignor to Bailey Meter Company, a corporation of Delaware Application October 27, 1931, Serial No. 571,427

16 Claims.

The present invention relates to combustion control systems, and has particularv reference to the control of combustion automatically in those furnaces fired by stokers, whereon a fuel bed presents a storage of fuel or a latent storage of heat at all times.

In such furnaces the fuel bed may offer considerable resistance to the passage of air for combustion due to an excess quantity of fuel on the stoker, a matted or packed and coked condition of the fuel, or through the presence of clinkers, ash or refuse, all of which may prevent the free passage of air. The fire may be too readily adapted to the passage of air through the presence of only a thin fuel bed or because of holes in the fire, uneven distribution, etc.

I have found that in the operation of furnaces, regardless of the fuel burned, a primary factor in the operation of the'furnace, (such for example as an indication of furnace output) is desirably used to actuate a primary control, and that such primary control must be effective upon-the element or elements of combustion most directly responsible for causing changes in the value of the primary factor. A parallel control of the remaining elements of combustion may be effected from the primary factor, or secondary control of such elements of combustion may be initiated responsive to variations in secondary factors in the operation of the apparatus, such as efficiency of operation of the furnace or conditions in the furnace such as temperature, etc.

The furnaces with which my control system is applicable are those in which the elements of combustion combine for the heating of vapor generating boilers or other purposes, but the embodiment of my invention which I have illustrated and will describe is in connection with vapor generating boilers heated by furnaces. In such apparatus an indication of furnace output may be the pressure of the vapor generated, while an indication of furnace condition may be the temperature of the furnace, and an indication of furnace efficiency may be the relation between rate of flow of vapor from the boiler and rate of flow of air through the boiler.

I have found that in the combustion of fuels which are burned in suspension such as oils, gas or pulverized coal, the rate of supply of the fuel itself primarily controls the rate of heat liberation and consequently the output of the furnace. Where fuel is burned on a stoker, providing a fuel bed having a latent storage of heat, however, the condition is different, in that primarily a variation in the supply of air to thefuel bed results in a desired variation in rate of output by varying the rate of heat liberation. With a fuel bed offering considerable resistance to the passage of air therethrough, it is necessary when increased output is desired to increase the supply of air through the fuel bed and through the furnace, while with a fuel bed offering little resistance to the passage of air it is necessary to carefully control the air supply thereto to prevent burning holes in the fuel bed through which the air 35 would readily pass without aiding in combustion.

It is, however, necessary to cause a replacement to the fuel bed in desired rate of the fuel which has been consumed or is being consumed, so that while I primarily control the supply of air through the furnace in accordance with the value of a primary factor in the operation of the furnace, such for example as an indication of furnace output, I further cause the primary control to effect regulation of the rate of supply of fuel to the fuel bed. Such control of the rate of supply of fuel is, however, further subject to a secondary control responsive to a secondary factor in the operation of the furnace, such, for example, as furnace conditions or furnace efficiency. By such readjusting or secondary control of the supply of fuel I take into account fuel bed conditions which are reflected in the measure of emciency or conditions in the furnace.

One object of my invention is to provide a method and apparatus for the control of combustion in furnaces fired with solid fuel on a grate or stoker, wherein the primary control of the elements of combustion is from a measure of the output of the furnace.

Another object is to provide such a control wherein a secondary control from a measure of furnace or combustion efficiency is used to readjust the supply of one of the elements of combustion.

Still another object is to have the secondary control .effective upon the supply of fuel to the fuel bed.

With these and further objects in view, I will now describe in detail the embodiment of my invention which I have illustrated in the following drawings, in which: 7

Fig'. 1 is a somewhat diagrammatic sectional elevation of a combustion control system for a stoker fired furnace heating a vapor generator.

Fig. 2 is a diagrammatic representation of a fragment of Fig. 1 comprising a modification thereof.

Fig. 3 represents a further embodiment of the invention comprising a fragment of Fig. 1.

A Fig. 4 is a fragment of Fig. 1 embodying a further arrangement.

Fig. 5 is an enlarged view of the pneumatic tachometer indicated at '7 in Fig. 1.

In Fig. 1 I have shown a complete combustion control system for the stoker fired furnace of a vapor generator whereas in Figs. 2, 3 and 4 1 show only those parts of Fig. 1 which have been changed therefrom as I consider it unnecessary in Figs. 2, 3 and i to duplicate all of the parts of Fig. 1 which are identical in consideration of the four figures. In all four of the figures I intend that the furnace, the vapor generator, the stolrer and air and fuel feeding equipment shall be identical as representative of the invention and for the purpose of describing my invention.

Referring now in particular to Fig. 1, I show a furnace 1 arranged for heating a steam generator 2 through the combustion within the furnace 1 of fuel fed to a fuel bed 3 by a stoker 4. The stoker may be driven by any conventional means such as the electric motor 5 c ntinuously running, and whose speed is control ed by a rheostat 0 in the electric circuit. A pneumatic tachometer 7 driven by and with the stoker 4 serves to provide a measure of the rate of fuel feed to the stoker 3. The tachometer is of a type well known in this art, wherein (Fig. 5) a sprocket or other driven wheel 112 is continuously rotated by a chain or belt from the stoker i and rotates a shaft carrying an open ended tube 111 having a hollow "1 connection with a sleeving end of the pressure pipe 107 which leads to within a liquid sealed bell 108. The bell 108 is pivotally suspended from one end of a beam 109 pivoted intermediate its ends and carrying a liquid displacing member 110. The whole constituting a measuring device 34 wherein an extension 35 of the beam 109 cooperates with an index 36 to show in desired units the rate of speed of the stoker or rate of supply of fuel to the furnace.

In operation when the whirling tube 111 is rotated from and by the stoker 4, air is thrown out of its open ends, thereby creating a suction in the pipe 107 and beneath the bell 108, bearing a known relation to the rate of rotation of the tube 111. The relation is quadratic to the extent that a plotted curve between speed of rotation and suction is parabolic in shape. The displacer 110 is shaped to extract the function so that the indication of the pointer 35 relative to the index 86 will be in equal increments of rate of fuel supply or as desired. In the present embodiment, the indication relative to the index 36 is directly in rate of supply of fuel to the furnace and the vertical rod. 17 is similarly and simultaneously so positioned.

Air for combustion of the fuel is supplied below the fuel bed 3 through an opening 8 in the furnace wall, and its rate of supply is controlled by the suction exerted upon the furnace of a stack 9 having positioned therein a damper 10 through the agency of a stop-start-reversing motor 11.

Steam generated in the boiler 2 passes therefrom through a conduit 12 in which is positioned a pressure difierential creating device such as a flow nozzle 13 for causing a drop in pressure bearing a definite and known relation to the rate of flow of steam through the conduit and forming a measure of the steam outflow.

1. utilize the pressure of the steam in the conduit 12 as an indication of output of the generator and correspondingly of the furnace, to be desirably maintained at a uniform predetermined pressure from predetermined value.

.16, if in a position other than value. If the pressure of the steam in the conduit 12 deviates from the predetermined value, such deviation is indicative of an excess or deficiency in the liberation of heat within the furnace which is desirably to be corrected to return the pressure to the desired value.

I actuate with the steam pressure, a Bourdon tube 14 which through a pivoted link 15 results (on the drawings) in a vertical movement of a presser bar 16 relative to a periodically reciprocated member 17 and a pair of opposed stepped wedge-shaped members 18. Each of the wedgeshaped members 18 is adapted when moved to close-circuit a contact 19 or 20. Such closure is accomplished periodically through reciprocation of a cam 21 and. for a length of time proportional to the vertical position of the presser bar 16 relative to the wedges. If steam pressure is of the desired value, the presser pin 16 has its head lying opposite the center of the crossed wedges 18 and continued reciprocation of the member 17 by the cam 21 will not cause movement of the wedges 18 sumcient to close either the contact 19 or the contact 20. 1f steam pressure deviates from the predetermined value, however, the presser pin 16 moves vertically upward or downward relative to the wedges 18 and in amount proportional to the pressure. In other words, if the pressure, for example, is 10 pounds above predetermined value, the'presser pin will move downward to the bottom (on the drawings) of the versa. If the decrease in pressure is 5 pounds, then the presser pin head will be moved downward one-half the distance between the shown position and the position opposite the lowermost part of the wedge 18. Thus, the vertical positioning of the presser pin 16 is proportional to changes in fluid pressure and if the steps on the wedges are of equal height and the profile of the cam 21 is of a uniform rise nature, then the length of contact closure of either 19 or 20 for each revolution of the cam 21 will be directly proportional in time length to the departure of It is, however, possible, and may be desirable. to give the steps of the wedges other than equal height and the contour of the cam 21 other than an equal rise characteristic. The contactor in general is of the type disclosed and claimed in the patent to Hardgrove 1,804,336 granted May 5, 1931, and

wedges 18, or vice serves through the contactsv 19 and 20 to energize relays 22 and 23 respectively.

The relays 22 and 23, actuated responsive to a departure of steam pressure from a predetermined value, comprise a primary-control for the rate of feed of the elements of combustion to the furnace. For the relays and contractor I provide power wires 24., 25, the former connected by a conductor 25 with the reciprocating member 1'1, the pilot motor continuously running motor 29 and a pilot motor 30. Relay 22 is connected to power line 25 through conductor 28, while relay 23 is connected to power line 25 through conductor 27. The continuously running motor 22 periodically moves the cam 21 to a position wherein the presser bar that corresponding to a predetermined steam pressure, causes a closure of the contact 19 or the contact 20 for, the energization of the ralay 22 or relay 23. Assume, for example, that the relay 22 is energized, then circuit is completed for energizing the pilot motor 11 for rotation in one direction. Such circuit may be traced asfoliows: Power line 25, conductor 27, re.,.y 22, conductor 31, the motor 11,

11, the stoker drive motor 5, a

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memes conductor 26, power line 24. Simultaneously an energization of the relay 22 will result in an operation of the pilot motor through conductor 27, relay 22, conductor 33, pilot motor 30, conductor 26.

Thus it will be seen that if the steam pressure deviates from a predetermined value, causing a closure of the contact 19 or the contact 20, a rotation of the pilot motor 11 will be caused for a change in the rate of air flow through the furnace and simultaneously a rotation of the pilot motor 30 will be accomplished in proper direction for a variation in speed of the fuel feeding motor 5. Thus the primary control responsive to departure of steam pressure, as a measure of output, from predetermined value results in a parallel control of fuel and airsupplied the furnace, which variation in rate of feed for a given pressure change depends upon gear ratio, speed, etc. of the pilot motors and their connections to the fuel and air supplying means.

I indicate at 34 a meter of known type responsive to pressure applied to a liquid sealed bell from the pneumatic tachometer 7 to move an indicator 35 relative to an index 36 as a measure of the rate of supply of fuel to the furnace.

At 37 1 indicate a rate of flow meter for the steam leaving the boiler through the conduit 12. Such meter is illustrated as a known type having a variable diameter liquid-sealed bell adapted to move an indicator 33 over an index 39 to read directly in terms of rate of flow, taking into account the known relation between pressure differential across the nozzle 13 and rate of fluid flow therethrough.

At 40 I indicate an air flow meter connected to points in the boiler passage between which there is resistance to the flow of the products of combustion, thus producing a pressure differair, but all of the products or gases of cornhustion leaving the furnace through the staclr 9 and which are utilized for heating the generator 2 in their passage from the furnace to the stack. When the proper calibration and adjustments have been made, the air flow meter 40, by measuring the rate of flow of all of the air and prodnets of combustion leaving the furnace will indicate the rate of flow of air supplied for combustion.

l employ the three meters, namely the fuel flow meter 34, the steam flow meter 37, and the air flow meter ill, to obtain control constituting secondary control of the rate of fuel feed to the furnace. A contactor 43 positioned responsive to the three meters mentioned serves to complete circuit to the pilot motor so for varying the rate of feed of fuel to the furnace in accordance with the relation of the values indicated on the three flow meters independently of steam pressure, and subordinate thereto. I have illustrated the contact bar 43 as connected by a conductor at through normally closed contacts on relays 22 and 23 in series to the power line 25. Conductors 45 and 46 lead respectively from the two contacts .of the contactor 43, the first to a normally open circuit contact on the relay 23 and the latter to a normally open circuit contact on the relay 22, but directly connected to the motor 30 whose neutral is connected to the conductor 26 for return to the power line 24. Thus if the relays 22 and 23 are as shown in deenergized position, the actuation of the contactor 43 to close circuit in one direction or the other will result in a movement of the pilot motor 30 in proper direction for a variation in the rate of feed of fuel to the furnace. If, however, either of the relays 22 or 23 is energized, a circuit through the conductor 44 is opened, thus eliminating the possibility of circuit closure to the pilot motor 30 through the contactor 43 so long as either relay 22 or 23 is energized. Thus the contactor l3 is subordinate to the relays 22, 23 controlled from steam pressure.

I have illustrated mechanical linkage interconnecting the three flow meters 34, 37 and 40 to actuate the contactor bar 43 upon departure of relation between the flow meters from desired relation. For example, pivotally depending from the index 35 is a rod d7 pivotally connected at its lower end to one end of a beam 48 freely floating. Intermediate the ends of the beam 48 is a rod 49 depending therefrom and carrying an indicator 50 cooperating with an index 51. The lower end of the rod 49 is pivotally connected to the contactor bar 43 for movement thereof.

Depending from the indicator 38 of the flow meter 37 is pivotally connected a rod 52, and from the indicator 41 of the flow meter i0 is a rod 53. At their lower ends, the rods 52 and 53 are pivotally connected to opposite ends of a freely floating beam 54 intermediate the ends of which is suspended a rod 55 carrying an indicator 56 adapted to cooperate with an index 5.7. At the opposite end of the pivoted beam forming the indicator ll is suspended a rod 58. Between the lower ends of the rod 55 and the rod 58 is freely floating, pivotally connected thereto, a beam 59 from a point intermediate the ends of which is suspended a rod on carrying an indicator 61 adapted to cooperate with an index 62. The lower end of the rod is connected to the end of the floating beam l3 opposite that end to which is connected the rod 4.7 previously mentioned.

Connected to and moved by the rod 58 is an indicator 63 cooperating with an index 64, while pivotally connected to the rod 47 and pivoted intermediate its ends is an indicator 65 also coopcrating with the index 64-.

lldilv to read from the indices mentioned, i. e., from the position of an indicator relative to its related index, instantaneous values and relations of primary importance in the operation of the apparatus. For example, from the index 39 I read the rate of steam flow from the generator; from the index 42, the rate of air flow through the generator; from the index 36, the rate of fuel feed to the furnace; while from the index 57 the relation of air flow to steam flow. From the index 64 I read, by the relation therewith of the indicators 63 and 65, the relation between air flow and fuel subsequent time delay necessary to complete any reaction which was initiated by changes in rate of fuel feed, it is not desirable to wait until such reactions are accomplished to determine whether or not the change in rate of fuel feed has been of proper amount and direction. For this reason, after having made a change in the rate of supply of fueland air to the furnace through the contactor l8wfrom steam pressure, I compare the metered value of the rate of supply of fuel and air as on the index 64, and if such relation between metered values is not as desired, a closing of circuit of the contactor 43 will result for a readjustment of the rate of feed of fuel.

For example, in operation, if steam pressure decreases from predetermined desirable value, the Bourdon tube 14 will tend to move in a clockwise rotation, positioning the presser. bar 16 (upward in the drawings) to cause a closing of circuit of the contact 19 and correspondingly an energization of the relay 22 whereby the pilot motor 11 and the pilot motor 30 are energized for increasing the rate of supply of fuel and air to the furnace whereby through the increased supply of air to the fuel bed an increase in rate of liberation of heat will result, while utilized fuel will be replaced through the increased rate of supply of fuel.

The increase called for on fuel and air'through the pressure contactor 18 should result in an increased reading on the fuel feed index 36 and on the air flow index 42 in desirable amount and in desirable relation as indicated on the index 64. However, characteristics of motors, dampers, etc. will determine whether or not an equal amount of correction applied to the fuel and air feeding devices results in a desirable relation between the rate of increase of supply of fuel and air, and if such is not the case, then desirable indication will not be given on' the index 64. For example, assume that the increase of the rate of fuel feed was not as great proportionally to the increase of rate of air flow, so that the reading on the index 36 was not as great proportionally to the reading on the index 42, then the downward vertical motion of the rod 60 would have been greater proportionally to the upward vertical motion of the rod 4'7 then desired, and the rod 49 would be moved downwardly a proportionate amount, thereby causing a closure of circuit between the conductor 44 and the conductor 46 for a movement of the pilot motor 30 to readjust the rate of feed of fuel whereby the fuel feed meter 34 responsive to such increase would bring the indicator 65 in desired relation to the air flow indicator 63 and correspondingly the indicator 50 to desired position on the index 51 whereby when this is accomplished, circuit between the conductors 44 and 46 would again be opened.

It will be seen that through the agency of the fuel feed meter 34 and the air flow meter 40 a simultaneous correction of the rate of feed of fuel and air through the agency of the pressure contactor 18 will be readjusted to balance the feed of fuel to air regardless of characteristics of the different feeding devices or agencies.

My control system does not depend, however, entirely upon the mere balancing of the supply of fuel and air to the furnace, but desirably causes a further readjustment of the feed of fuel to satisfy a measure of .efiiciency of combustion secondary to satisfying the demand upon the furnace. It is a well recognized fact that in the operation of vapor generators such as the steam generator 2, a desirable relation will exist bememes tween the rate of flow of steam from the generator and the rate of flow of air through the generator at all rates of generator output, although not necessarily the same relation at all rates of output. I indicate, therefore, upon the index 5'? through the medium of the indicator 56 any departure from predetermined relation between a measure of the rate of steam flow and a measure of the rate of air flow, wherein instantaneous values of the two are applied to opposite ends of the beam 54 for vertical positioning of the rod 55 from predetermined desirable position. Thus if a greater excess of air is supplied to the furnace than is desirable for combustion, the indicator 56 will be caused to move upward on the index 5?, while if a deficiency of air is present, the indicator 56 will be moved downward on the index 5'? from desirable position. In either event the result is a positioning vertically of one end of the floating beam 59 and correspondingly of the rod 60', the beam 48, the rod 49 and the contactor 43. Thus in operation, if the steam flow-air flow relation is not as desired, a closure of circuit between the conductor 44 and either the conductor 45 or 46 will occur through the medium of the contactor 43 for a readjusting positioning of the pilot motor 30 whereby the fuel bed will be thickened or thinned through a change in the rate of feed of fuel and thus for an output-controlling rate of supply of air, the thickness of the fuel bed will be properly adjusted to satisfy not only demand upon the furnace as indicated by steam pressure, but also efilciency of combustion as indicated by relation between steam flow and air flow.

It will be seen in general, then, that the contactor 43 is controlled for a readjustment of rate of fuel feed from a relation between. air flow and fuel feed with such relation modified by a relation between steam flow and air flow or a measure of furnace efiiciency. In Fig. 2 I show the linkage of Fig. 1 except that the rod 53, the beam 54 and. the rod 55 have been eliminated, and for the rod 52 has been substituted a rod 52A,

.while for the beam 59 I have substituted a beam 59A. Otherwise the linkage connection between the three meters is the same as in Fig. l, and the contactor 43 remains the same. The action and result as to variation or readjustment in the rate of supply of fuel is as that described for Fig. 1, but I have somewhat simplified the linkage from a practical standpoint, although I feel that the linkage as shown in Fig. 1 illustrates more clearly the inter-relation between air flow, fuel feed and the steam flow-airflow relation or measure of emciency.

In Fig. 2 the rod 60 is positioned vertically and in the same direction by both steam flow and air flow, while the rod 47 is positioned oppositely by a measure of fuel feed. The direction of motion is such that if the three measures are the same or in desired relation, then the indicator 50 remains at a neutral position and no circuit is completed through the contactor 43. If, however, the relation between fuel feed and airflow departs from. that desired, there will be a vertical positioning of the rod 49. Likewise if the relation between steam flow and air flow departs from that desired, there will be a vertical positioning of the rod 49, and if the relation between fuel feed and the relation of steam flowair flow departs, there will be, a vertical positioning of the rod 49, all relative to a desired position. 1

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In Fig. 3 I illustrate the same arrangement as in Figs. 1 and 2, except that I substitute for the steam flowair flow relation as a measure of furnace efficiency, an indication of the constituents of the gases leaving the boiler. I replace in this illustration the steam flow meter 37 by a commercial device 66 connected by a pipe 67 to the outlet of the generator and responsive to the percentage of the constituents of the flue gases for positioning an indicator 38A over an index 39A relative to predetermined value.

In Fig. 4 I utilize as a measure of furnace condition, the temperature within the furnace, indicating the same by means of an indicator 38B upon an index 39B through motion produced by a device 68 connected by the wires 69 to a temperature responsive device such as a thermocouple 70 positioned sensitive to the heat of the furnace.

In ge eral, in the various embodiments illustrated and described, I provide a furnace control of combustion, primarily for fuels burned on a fuel bed, wherein is a storage of fuel and correspondingly of latent heat. Such a combustion control system having a primary control of the air supplied to the furnace from an indication of demand upon the furnace, such for example as the pressure of steam at the outlet of a steam generator being heated by the furnace. In parallel with the control of air I provide from the steam pressure indicator a control of fuel feed to the furnace to replace to the fuel bed that latent heat which was liberated through combustion.

I provide secondary control of one of the elements of combustion, desirably the fuel feed, upon departure of a balance between a measure of the rate of feed of air and the rate of feed of fuel.

I provide further a secondary adjustment upon the rate of feed of fuel to the furnace, responsive to a measure of furnace efficiency such, for example, as the steam iiowair flow relation, a measure of the composition of the gaseous prodnets of combustion, or an indication of temperature within the furnace.

I provide that such measure or indication of furnace efficiency or, desirable furnace operation may modify the balance between air flow and fuel feed before becoming effective upon the rate of fuel feed.

I further provide with my system an arrange-= merit whereby the primary control from an indication of furnace demand takes precedence over the secondary control.

It will be understood that I have illustrated and described known types of furnace and boiler construction as well as feeding means for the elements of combustion, and lmown mechanisms for the measurement and control of same.

It is not essential with my invention that the furnace be used for heating a vapor generator, as such furnace might be used for metallurgical work or other desirable service. Neither is it necessary that the type of meters and control mechanisms which I have shown be utilized, for the invention contemplates broadly a method of operation which may be accomplished automatically through the agency of measuring devices respon= sive to variable factors for giving indications which may be visual or used in combination to effect controls.

It will be understood that bydescribing and illustrating certain preferred embodiments of my invention, I am not to be limited thereby except Thus' at to the claims appended hereinafter in view of prior art.

What I claim as new, and desire to secure by Letters Patent of the United States, is:

1. The method of controlling the operation of a furnace heated by elements of combustion, which includes the steps of normally controlling the supply of elements of combustion in accordance with a measure of furnace output, and readjusting the supply of one of. the elements of combustion in accordance with the relation between a measure of furnace efliciency and a measure of each of the elements of combustion.

2. The method of controlling the operation of a furnace heated by elements of combustion, which includes the steps of normally controlling the supply of elements of combustion in accordance with a measure of furnace output, and readjusting the supply of at least one of the elements of combustion in accordance with the relation between a measure of furnace condition and a measure of each of the elements of combustion.

3. The method of controlling the operation of a furnace heated by elements of combustion, which includes the steps of normally controlling the supply of elements of combustion in accordance with a measure of demand upon the furnace, and readjusting the supply of at least one of the elements of combustion in accordance with the relation between a measure of furnace condition and a measure of each of the elements of combustion.

4. The method of controlling the operation of a vapor generator having a furnace heated by elements of combustion, which includes the steps of normally controlling the supply of elements of combustion from an indication of static pressure in the vapor outflow, and readjusting the supply of one of the elements of combustion in accordance with the relation between a measure of each of the elements of combustion.

5. The method of controlling the operation of a vapor generator having a furnace heated by elements of combustion, which includes the steps of normally controlling the supply of elements of combustion from an indication of vapor outlet pressure, and readjusting the supply of one of the elements of combustion in accordance with the relation between a measure of furnace condition and a measure of each of the elements of combustion.

6. The method of controlling the operation of a vapor generator having a furnace heated by fuel and air supplied for combustion, which includes the steps of normally controlling the supply of fuel and air from an indication of static pressure in the vapor outflow, and readjusting the supply of fuel in accordance with the relation between fuel supply and air supply.

7. The method of controlling the operation of a vapor generator having a furnaceheated by fuel and air supplied for combustion, which includes the steps of normally controlling the supply of fuel and air simultaneously from an indication of static pressure in the vapor outflow, measuring the rate of supply of fuel, measuring the rate of supply of air, obtaining the ratio between such measures, comparing such ratio with a predetermined ratio, and readjusting the supply of fuel in accordance with such comparison.

8. The method of controlling the operation of a vapor generator having a furnace heated by fuel and air supplied for combustion, which includes the steps of normally controllingthe sup- Mil (g ply of fuel and air from an indication of vapor outlet pressure, and readjusting the supply of fuel in accordance with the relation between a measure of furnace efficiency, fuel supply, and air supply.

9. The method of controlling the operation of a vapor generator having a furnace heated by fuel and air supplied for combustion, which includes the steps of normally controlling the supply of fuel and air from an indication of vapor outlet pressure, and readjusting the supply of fuel in accordance with the relation between a measure of furnace condition and the relation between fuel supply and air supply.

10. The method of controlling the operation of a vapor generator having a furnace heated by fuel and air supplied for combustion, which includes the steps of normally controlling the supply of fuel and air from an indication of static pressure in the vapor outflow, and readjusting the supply of fuel in accordance with the relation between vapor outflow, fuel supply, and air supply.

11. The method of controlling the operation of a vapor generator having a furnace heated by fuel and air supplied for combustion, which includes the steps of normally controlling the supply of fuel and air in parallel from an indication of vapor outlet pressure, and readjusting the supply of fuel in accordance with the relation between a measure of the CO2 content of the gaseous products of combustion, a measure of fuel supply, and a measure of air supply.

12. The method of controlling the operation of a vapor generator having a furnace heated by fuel and air supplied for combustion, which includes the steps of normally controlling the supply of fuel and air in parallel from an indication of vapor outlet pressure, and readjusting the supply of fuel in accordance with the relation between a measure of the constituents of the gaseous products of combustion, a measure of the fuel supply, and a measure of the air supply.

memes 13. The method of controlling the operation of a vapor generator having a furnace heated by fuel and air supplied for combustion, which includes the steps of normally controlling the supply of fuel and air from an indication of vapor outlet pressure, and readjusting the supply of fuel in accordance with the relation between an indication of furnace temperature and a relation between fuel supply and air supply.

14. The method of controlling the operation of a vapor generator having a furnace heated by fuel and air supplied for combustion, which includes the steps of normally controlling the supply of fuel and air from an indication of vapor outlet condition, readjusting the supply of fuel in accordance with the relation between a measure of fuel supply and air supply, and allowing the controlling to take precedence over said readjustmg. i

15. The method of controlling the operation of a vapor generator having a furnace heated by fuel and air supplied for combustion, which includes the steps of normally controlling the supply of fuel and air in parallel from an indication of vapor outlet condition, readjusting the supply of fuel in accordance with the relation between a measure of furnace condition, a measure of fuel supply, and a measure of air supply, and allowing the controlling to take precedence over the readiusting.

16. In a combustion control system for a furnace adapted to heat a vapor generator, in combination, fuel supply controlling means, air supply controlling means, indicating means responsive to demand upon the furnace and adapted to actuate both fuel supply controlling means and air supply controlling means, an air supply meter, a fuel supply meter, measuring means of furnace efilciency, and means responsive to both -meters and to said measuring means and adapted to readjust the fuel supply controlling means.

PAUL S. DICKEY.

cntttttcltt or connection.

Patent No. tattoos.

no it, on.

l AlUL S. llllllillll.

lt is liereby certified that error up above numbered potent requiring correctio insert at least; and line it Patent should be read with these corrections l, before "one" least"; i that the said lettere peers in the printed specification oi the n as iollows: U

, claim 3, strike out the words "at i age 5, line 85, claim therein that the some may conform to the record of the case in the Patent (mice. A. D. i934,

Signed t1 sealed this lltli tiny of September,

iScci) lesl ie Frazer issioner of Patents.

Hit 

